Down but not out.

A 20-year-old Hispanic man with Down syndrome presented with progressively worsening headache, fluctuating decreased vision, and bilateral optic disk edema. Magnetic resonance imaging of the head showed an empty sella, and magnetic resonance venography showed thrombosis of left transverse and sigmoid sinuses. Catheter angiography angiogram showed a dural arteriovenous fistula in the wall of left transverse and sigmoid sinuses. The patient underwent Onyx endovascular embolization of the fistula, resulting in its angiographic obliteration, followed by resolution of his clinical signs and symptoms.